The present invention relates to the control of the plug or stopper for the casting outlet of a casting vessel such as a tundish particularly of the type which cooperates with a mold or molds for continuous casting.
The German printed Patent Application 2,435,485 discloses a control in which the level of the bath of molten metal in a machine for continuous casting is monitored, and electrical signals are provided being indicative of the level and of any changes of that level therein. The signal is used to raise or lower a plug which controls the casting outlet of a tundish which feeds molten steel into a mold.
Independent from the foregoing, it is generally known to construct and to mount a tundish feeding a mold for continuous casting, to be displaceable; that is to say, the tundish may, for example, be constructed for being lifted or lowered and for being laterally displaceable or pivotable. Thus, there is no fixed association and connection between tundish and mold. Rather they are mounted for a relative and independent displacement. This is particularly important in the case of sequence casting in which the tundish wears rather rapidly, is more easily damaged and subjected to other interferences as well, all of which being instances which require more or less rapid and more or less frequent exchange of the tundish.
This independence of tundish and mold(s) is operationally not maintained if a closed loop control is included for lowering and raising the plug. Such closed loop requires electrical, mechanical and/or hydraulic connection of the tundish with associated equipment and of the casting stand, particularly the mold, because the plug is part of the tundish and at least some of the control apparatus including particularly the device monitoring the level of the bath in the mold is inherently structurally combined with the mold. Thus, whenever the tundish is to be replaced these connections must be interrupted. If one considers further that a tundish usually does not just feed a single mold but several, possibly even many molds each of them requiring its own control loop, one can readily see that the total amount of mechanical, electrical, and/or hydraulic connection is significant and errors are more likely to occur upon reconnecting the system. Another aspect is that the actuating mechanism for the plug such as a hydraulic drive being in physical proximity of the casting process is very much endangered for a variety of reasons, such as sputtering off steel, heat, etc.